Fluoride and IQ – another study coming up

It’s basically a systematic review of published scientific literature on fluoride-IQ effects in humans. It’s just at the planning stages and don’t expect anything for a few years – peer review and public consultation of the findings are not planned until 2018.

Some might question whether such a review will add anything – after all this question has been included in several reviews of possible health effects of community water fluoridation (eg NRC and NZ review), although it has just been one component of most of these reviews. An exception is the review by the Bazian Company

This considered in detail the specific publications used by campaigners against CWF to argue there is a problem (the reviewers found there wasn’t).

But, on the positive side, this will most likely be one more review by a reputable body showing how poor the evidence used by anti-fluoride campaigners is. On the negative side the process and findings will be misrepresented again and again by anti-fluoride campaigners. That has already started – see the press release by Fluoride Free NZ – Fluoride-Brain Studies Set to Expose Fluoridation Damage. Talk about counting chickens before they hatch!

“The National Toxicology Program (NTP) proposes to conduct an evaluation of the published literature to determine whether exposure to fluoride is associated with effects on neurodevelopment, specifically learning, memory, and cognition. This evaluation will use systematic review methods and include an examination of data from human (epidemiological), experimental animal, and mechanistic studies. Previous evaluations have found support for an association between fluoride exposure and impaired cognition; however, many of the studies included exposure to high levels of fluoride. Most of the human evidence was from fluoride-endemic regions having high background levels of fluoride, and the animal studies typically included exposure during development to relatively high concentrations of fluoride (>10 mg/L) in drinking water. Thus, the existing literature is limited in its ability to evaluate potential neurocognitive effects of fluoride in people associated with the current U.S. Public Health Service drinking water guidance (0.7 mg/L).” [My emphasis].

The proposal also says:

“A 2015 systematic analysis of the human literature conducted for the Republic of Ireland’s Department of Health (Sutton et al. 2015) concluded that there was no evidence of an association with lowered IQ in studies of community water fluoridation areas based primarily on an analysis of a prospective cohort study in New Zealand (Broadbent et al. 2015). For fluoride-endemic areas, there was a strong suggestion that high levels of naturally occurring fluoride in water (> 1.5 ppm) may be associated with negative health effects, including lowering of IQ. In general, these studies were considered of low quality because they did not fully account for other factors that could also cause a lowering of IQ e.g., nutritional status, socioeconomic status, iodine deficiency, other chemicals in the ground water (arsenic or lead). The conclusions of Sutton et al. (2015) are consistent with findings of a 2012 meta-analysis of 27 epidemiology studies that “supported the possibility of an adverse effect of “high” fluoride exposure on children’s neurodevelopment, specifically for lowered IQ; although the 2012 meta-analysis also identified study quality limitations, mostly related to reporting quality, that limited the strength of conclusions that could be reached (Choi et al. 2012).

The anti-fluoride spin

You wouldn’t think the anti-fluoride crowd would welcome such a careful analysis of the poor-quality articles they promote – but you can get some idea of how they will spin this study over the next few years from the comments in the above press release:

“Results could mean the end to fluoridation world-wide, and definitely should put a halt to any plans to start fluoridation in places not currently fluoridated.

Because it is now well established that fluoride affects the brain, the NTP plans to conduct new animal studies to determine the lowest dose at which this damage occurs. They also plan to do a systematic review of all the existing scientific literature. To date, there have been 314 studies that have investigated fluoride’s effects on the brain and nervous system. These include 181 animal studies, 112 human studies, and 21 cell studies.”

The confirmation bias and dogmatic agenda stick out like a sore thumb – don’t expect these people to accurately report this study’s findings.

“many of the studies included exposure to high levels of fluoride. Most of the human evidence was from fluoride-endemic regions having high background levels of fluoride,”

As with elections “most” or “majority” means over half. Of course there are lots of studies when people are obviously sick. That should not take weight away from the subset with lower levels.

“For fluoride-endemic areas, there was a strong suggestion that high levels of naturally occurring fluoride in water (> 1.5 ppm) may be associated with negative health effects, including lowering of IQ. In general, these studies were considered of low quality because they did not fully account for other factors that could also cause a lowering of IQ e.g., nutritional status, socioeconomic status, iodine deficiency,…”

Dishonest since cannot use results of sufficient iodine areas for iodine deficiency groups which exist in pregnancy and for the many who escape the supplementation programs for various reasons.

“other chemicals in the ground water (arsenic or lead).” Nor did Broadbent for their 99 control subjects. Corrosion control came in with fluoridation in Dunedin, and unfluoridated Mosgiel where control subjects may have lived did not get corrosion control until 1990s/early 2000 upgrade. It was aimed at copper/brass corrosion and brass taps often have lead with the copper and zinc alloy which brass is.

The IQ studies Connettâs crowd rely on were almost all from areas of endemic fluorosis. Of course the Broadbent study wasnât â and is probably the only study relevant to CWF.

I think the systematic review will find all the studies Connett relies on are of very poor quality. In fact the only one which included a correlation found fluoride contributes only a very small amount to the variance in IQ. This suggests confounding factors are very important and makes studies which donât properly include these (none of the ones by Connett do) very suspect.

The statement about the studies is factual. For you to call it âdishonestâ Brian, only shows how biased you are. You are going to be one of the first to reject the findings of this review, I predict.

Broadbent found no effect of F on IQ so resorting to bitching about confounding factors is really lame. You have to perform quite a bit of mental gymnastics to drag that argument in. Broadbent actually did including many possible confounding factors in their statistical analysis â the Chinese studies Connett relies did not include any of these in a similar proper statistical analysis.

“(This is/This may be/This may not be/This isn’t) Dishonest since (I/we/you/they/he/she) cannot use (the/any/many/none) (of the/of any/of many/of any of the) results of (in) sufficient iodine (supplemented) (intake) areas for iodine deficiency groups which (may/may not) exist in pregnancy and for the many (others/groups/societies) who (may/may not) escape…”

Please complete your sentences so that we know exactly what you are saying and do not have to make any assumptions or guesses.

Clarity in science has major benefits. In contrast, obfuscation tends to make readers ignore papers or comments.

To argue (I think) that the Chinese papers are more accurate because they did not include confounding factors, and that Broadbent’s paper is inaccurate because confounding factors were considered, is contrary to all I understand about statistics and populations.

No, Pete – it would be impossible to include the infinite number of logically possible confounding factors in a statistical analysis. But Broadbent et al did include the relevant ones.

In contrast, the studies that the “Connett crowd” rely on did not include any other factors at all in the very few regression analyses they performed. The data from Xiang showing that F contributed only 3% to the variance in IQ is a strong indicator that ither factors are involved – F can ony be a very minor factor and once the others are considered it is most likely it would not contribite anything to the variance in IQ at all.

Pete, that’s correct. For one thing Broadbent et al did not take into account the iodide in drinking water difference between Otago and other parts of NZ. So even *if* it works for Otago its findings cannot be applied in Canterbury.

Those unfortunates who miss optimum iodine from supplementation would be likely to be worse of from fluoridation if it were imposed on Canterbury.

Ken keeps on repeating the Xiang 3% explanation of fluoride on IQ, and I keep on repeating that Xiang’s study was done by removing the confounding iodine factor by having the study only compare iodine-sufficient communities. That is not a reality for NZ.

I wrote: “Corrosion control came in with fluoridation in Dunedin, and unfluoridated Mosgiel where control subjects may have lived did not get corrosion control until 1990s/early 2000 upgrade.”

Stuartg is criticising my use of “may”.

Broadbent did not specify the unfluoridated suburbs except to say: “However, suburbs
with CWF were mostly located in central Dunedin,
and those without CWF were satellite suburbs.”

Mosgiel is an unfluoridated suburb of Dunedin.

I got this from the Dunedin CC water engineer:
“From memory, the DCC used to have to monitor lead levels in the main Metropolitan distribution system watermains up until the late 1990’ earlier 2000’s due to the corrosiveness of the water coming from the Mt Grand and Southern water treatment plants. These were and are fluoridated though. Following an outbreak of accelerated premature copper hot water cylinder failures, a lot of work was put into optimising the treatment process including pH and alkalinity control to reduce the corrosiveness of the water. Work over many years on corrosion control has meant that the DCC were allowed by the regulator to cease lead monitoring.

The one non-fluoridated area where corrosion control treatment system upgrade work occurred was in Mosgiel. The problem being targeted was corrosion of copper pipes and brass fittings. Lead was not seen as a problem although some would have been released from corroded brass fittings. Once again the new treatment systems were installed in the 1990’s and up graded again in the early 2000’s.

Other outlying systems which feature corrosion control treatment processes are Outram, West Taieri, Waikouaiti & Port Chalmers. The small Outram plant has had corrosion control in place since it was built by the old County Council. The West Taieri and Waikouaiti WTPs were upgraded about 7 years ago and both plants feature pH and alkalinity control systems. I note that the Port Chalmers plant is only run over the system to assist the supply from Mt Grand.

The concern that using fluorosilicate additives to fluoridate drinking water causes water system pipes to corrode is not supported by science. At the level recommended by the U.S. Public Health Service for fluoridation of public water supplies (0.7 to 1.2 mg/L, or parts per million), the fluoride ion has little influence on either corrosion or on the amounts of corroded metals released into the water. Fluorosilicates contribute to better water stability with less potential for corrosion, because silica stabilizes the pipe surface.
CDC. Corrosion in Pipes

Brian, you are indulging in extreme straw clutching in an attempt to discredit Broadbent’s high-quality work, while at the same time putting extreme faith in Lin’s newsletter article which is of poor quality.

Xiang did not “remove” any confounding factors all – and didn’t check for any (although I suspect he probably could have). Connett is silly to claim otherwise – simply determining average values for a village is not the same as a multiple regression. Connett makes a big thing of the significant correlation of IQ with urinary F (never revealing it explains only 3% of the variance. But, in fact, Xiang did not do any multiple regressions, let alone include I as a factor. So he did not check for confounding factors in his regression at all.

If a community suffers from I deficiency then the obvious answer is to increase dietary I – not pretend it is caused by something else.

chris price: “The concern that using fluorosilicate additives to fluoridate drinking water causes water system pipes to corrode is not supported by science.”

There is a concern about leaving water too acid when its going to be fluoridated. So the acidity is reduced by the engineer.

As the engineer said the Mt Grand and Southern water treatment plants had to have that corrosion control. There had been lead in the water until then. They kept on doing lead measurements on Dunedin water, it appears, until the corrosion control was added to the non-fluoridated water, too, around 2000.

So the subjects who were now adult and had grown up in non-fluoridated areas would have likely been exposed to more lead so Broadbent should have noted that.

So now we have the Masters and Coplan paper and the Hirtzy comment quiety as evidence,And then blame the Broadbent paper for not pursuing it. If you want to quote a paper why not do it
Could it be that these papers were not valid evidence,and were revoked by Urbanskey and Schock

The EPA similarly found that Hirzy’s claim that fluorosilicic acid caused leaching of lead from pipes in the water supply system was similarly unproved”

That is more than the sufficiency level for iodine suggested in this FAO report, so it would be expected for fluoride to have less effect. And it would not be up to the level where high iodine starts to produce thyroid trouble exacerbated by fluoride.

By not measuring in a low iodide area Xiang has avoided that confounding factor.

“Moulopoulos et al. (21) reported that a urinary iodine excretion between 151 and 200 µg/g creatinine (1.18-1.57 mmol/g creatinine), corresponding to a concentration of about 200 µg/l (1.57 mmol/l), gave the lowest values for serum TSH in a non-goitrous population” http://www.fao.org/docrep/004/y2809e/y2809e0i.htm

The fact remains, Brian, that Xiang did not check for any confounding factors in his regression – none at all, despite Connett’s claim. And clearly there was a good range of I values to enable inclusion in a multiple regression. (Most probably if that had been included, and perhaps a few more other factors, the relationship with F would have been non-significant).

You are relying on a poor quality paper (where there was no significant correlation shown with I) to postulate that a poor relationship with F is explained by I. You are doing the same with Pb for Broadbent’s paper. All this is extremely speculative and defensive. Go ahead and produce data to support you spurious claims – but until then your ideas are no better than all the manipulations introduced into the geocentric solar system model to explain its failures. And they are evidence free.

You are putting lipstick on a pig. And accusing reputable researchers of dishonesty when their summary of the literature embarrasses you.

Let’s go back to how I used the word, “dishonest,” as I smile back at you with that word you have used against me.

I quoted and wrote: ““For fluoride-endemic areas, there was a strong suggestion that high levels of naturally occurring fluoride in water (> 1.5 ppm) may be associated with negative health effects, including lowering of IQ. In general, these studies were considered of low quality because they did not fully account for other factors that could also cause a lowering of IQ e.g., nutritional status, socioeconomic status, iodine deficiency,…”

Dishonest since cannot use results of sufficient iodine areas for iodine deficiency groups which exist in pregnancy and for the many who escape the supplementation programs for various reasons.”

Well perhaps only mistaken.

They give the impression the IQ trouble was only a result of low iodine in that case, therefore fluoride is just great for everyone.

They are not scientific if they are just two-valued, “it’s not fluoride caused low IQ, it’s low iodide.”

There is a third factor that the halides, fluoride and iodide, may be dancing with one another, and one may fall over.

“the halides, fluoride and iodide, may (or may not – my addition) be dancing with one another,…”

So may, or may not, the fluorides chloride, bromide and astatide. You didn’t mention them.

The concentration of chlorides in tap water overwhelmes the concentration of fluorides and iodides. If there was a clinically relevant interaction between the halides in tap water then chloride would overwhelm the rest because of its concentration.

So why are you not challenging chlorides? Or bromides? Or astatides? I suspect that it’s because there is no reliable evidence that any of the halides (including fluoride and iodide) cause problems in humans at the levels found in tap water.

It is dealing with greater fluoride levels, but I cite it since a mechanism is appearing. At the end of the second page it says the fluoride is not affecting TSH, made by the pituitary gland when it wants more thyroid hormones T3 and T4 to be made, but is reducing T3 and T4. The pituitary should then be responding but it isn’t. Is it that what fluoride is doing is making something which looks to the pituitary like T3 and T4?

I shall extend on my “note form” comment. As I said to Ken he sometimes calls me dishonest.

I quoted: “For fluoride-endemic areas, there was a strong suggestion that high levels of naturally occurring fluoride in water (> 1.5 ppm) may be associated with negative health effects, including lowering of IQ. In general, these studies were considered of low quality because they did not fully account for other factors that could also cause a lowering of IQ e.g., nutritional status, socioeconomic status, iodine deficiency,…”

Those two sentences could be (mistakenly?) read as meaning in part that when the scientists did not fully account for iodine deficiency, their studies would be low quality, meaning that IQ would probably not be being lowered by the fluoride >1.5 ppm. Though they have not actually said that.

Now they have said, “also cause,” and some readers may think they mean, “instead cause.” Though I am stretching that a bit. “Also’ is often used like “instead” in such expression. So I won’t dwell on that.

Now as I pointed out about Xiang’s study, they held iodine optimum, and they got very little effect of fluoride consequently. Is that the sort of study which THE PROPOSAL intends? If it is then the results of the study should not be applied to populations without optimum iodine. To me that looks very wrong to spend the study money proving fluoridation is OK for a hypothetical group, and leaving out important groups like pregnancy and people who keep off bread if gluten intolerant and salt if they have blood pressure. I used the word “dishonest,” and if it is not dishonest I think it needs defending at least. Pregnancy is a time when brains are forming.

They do not actually exclude the concept of possible interaction between fluoride and iodide as a low IQ cause, but they are implying in my view that whatever is happening, if it is low iodide then they can happily forget about it. To me it gives the impression that their minds may be made up already.

Better than what I wrote in note form?:

“Dishonest since cannot use results of sufficient iodine areas for iodine deficiency groups which exist in pregnancy and for the many who escape the supplementation programs for various reasons.”

Brian – No, they didnât say that, and yes you are stretching it (more than) a bit.

No, Xiang did not âhold iodine optimum.â They did not manipulate the I at all â accepting the values as they were. These values covered quite a range but they did not include I in their regression (possibly because to do so would have removed any significance from the slight correlation with urinary F.

You should read the proposal â of course they are not intending to replicate a study like Xiangâs or anyone elseâs. They will simply be reviewing such papers, establishing their problems and quality, and making an overall assessment from this review and their similar review of animal studies. They also plan to fill in some gaps with animal studies (mainly the lack of anything covering low concentrations) although commenters were rather cynical about what that would achieve because of difficulties.

I find it interesting you are putting so much faith in Linâs newsletter article of one and a bit pages. You have nothing else for your rants about iodine/fluoride (except one or 2 equally bad studies from China). Your idol Paul Connett actually refuses to base his claims in that paper but relies instead on Xiangâs papers which he thinks far more reliable. It is also interesting that you acknowledge Xiang actually found very little correlation with F â yet if you used the same criteria as you do with Lin (pointing to the significant difference in IQ of two villages) you would be supporting Connett on this. The regression analysis of Xiang convinces you that the effect of F is miniscule and possibly not real. Lin did not find any correlation with F in the one regression analysis they did (or at least didnât report one).

In contrast, you found a correlation (with a correlation coefficient of 1.0!) â but then again you used just 2 data points! I was going to say that not even Paul Connett is that stupid â but actually that is exactly what anybody is doing who simply relies on a significant difference in IQ between 2 villages and that is exactly what Connett does with his use of the poor quality Chinese studies.

To Make matters worse, we would not be discussing these Chinese articles were it not for the fact that a politically and ideologically motivated body hinted down the papers, translated them and made them available in their pet âscientificâ journal. If only all the obscure Chinese, Byelorussian, Ukrainian, North Korean, etc., papers could be made available to us in this way.

Then again, the only really reliable paper not âdiscoveredâ in this way â Broadbent et al â does not fit the motivations of this group and so must be coindemned.

Ken wrote: “No, they didnât say that”
I copied it from what you wrote the paper also said.
Ken wrote: “No, Xiang did not âhold iodine optimum.â They did not manipulate the I at all â accepting the values as they were. These values covered quite a range”

By not looking for groups displaying the usual range of normal, low and high iodine segments they were manipulating the I, in my viewpoint. Like a lawyer challenging which jury members.

Referring back to Lin FF, I have found possible brick tea drinking by children in West China. The graph of fluorosis vs mg/kg intake is not a straight line but has a rather sudden jump or change of slope. It is possible that the strong tea, if they drink it, brings the children closer to the jump, so smaller amounts in water could take them up the jump.

I am looking for more data on serum fluoride levels and how they drop, or vary over 24 hour depending on frequency of tea consumption, frequency of water consumption, frequency of toothpaste ingestion, or absorption in the mouth. Just the total daily dose I do not think would be adequate to use in studies. Things need to change in human metabolism. For example, in eating, starch is mixed with salivary enzymes in the mouth and begins to be converted. When the food goes to the stomach it dilutes the acid and the salivary enzymes can only work until the stomach replaces the acid over an hour or so. So I wonder if the body can cope with constant fluoride intake or whether variation is needed. When it is in water that is not so possible. Mouth absorption needs more study, too.

I wrote: “Ken keeps on repeating the Xiang 3% explanation of fluoride on IQ, and I keep on repeating that Xiang’s study was done by removing the confounding iodine factor by having the study only compare iodine-sufficient communities. That is not a reality for NZ.”

Ken can’t argue with the substance of what I am saying, therefore has to make a lot out of my poor syntax instead.

I’ll say it again:
Xiang’s study compared the iodine-sufficient communities of Wamiao and Xinhuai. So the confoundment of low iodine cannot be seen and the study cannot apply to NZ,

Ken wrote: “You said this – not me. It is dishonest and does not represent the proposal at all”

I had written: “They give the impression the IQ trouble was only a result of low iodine in that case, therefore fluoride is just great for everyone.”

So Ken are you proclaiming the IQ trouble was NOT a result of low iodine (of course extra lead &c.) instead of fluoride? And that therefore it is NOT OK for people to think fluoride is generally acceptable?

Xiang wrote:
“Results and Discussion
• No significant differences were found
between the two village in the levels
of iodine in the urine and lead in
blood of the children.
• Thus urinary iodine and blood lead
levels do not appear to affect the
differences in IQ in children between
the two villages.”

âXiang’s study cannot be generalised to a world in which iodine levels do vary.â

I agree completely, and quite irrespective of iodine levels.

Yet your mates Paul and Michael Connett are doing exactly that. Xiangâs work is a key element in their programme and in the so far unpublished paper by Connett, Hirzy et al., claiming to show fluoridation should be stopped.

And the new dogma of FAN is âMichael is an expert on both the IQ and animal neurotoxicity studies.â

Also, this point about iodine really undermines the paper of Peckman et al, doesnât it? You know, the paper you have been promoting.

We don’t know what a Xiang study would have shown had it encompassed varying iodine levels. Though we can get a direction to look from Lin FF.

And you wrote: “Yet your mates Paul and Michael Connett are doing exactly that. Xiang’s work is a key element in their programme and in the so far unpublished paper by Connett, Hirzy et al., claiming to show fluoridation should be stopped.”

Xiang’s study is interesting because it shows a significant though small fluoride IQ negative correlation even when iodine averages are close.

For a moment let’s think of any relationship between children’s hunger and their parents’ income. A small negative overall correlation may show in a relatively wealthy society. Say 85% of incomes are sufficient. The poverty of the 15% won’t show much in the overall correlation, it will only affect it a small amount.

Connett thinks a parallel thing is happening in Xiang’s figures so divides the UF levels into categories, because the 15% minority should not be written off.

Brian, please link me to where Connett âdivides the UF levels into categoriesâ â have yet to see this. From memory, Connettâs only mention of urinary F is to state there is a significant correlation with IQ. He doesnât even provide an R2 value â for obvious reasons.

That referred to the misleading graph using water F – not urinary F. And this was prepared by Xiang, not Connett – although it is the one Connett relies on in his campaign. It is misleading and dishonest.

Brian, I see your willingness to abandon rational understanding of the data. But at the same time, I agree it would have been nice to have seen inclusion of parental incomes and child hunger in the regression analysis. I suggest inclusion of a few items like this would have removed any significance attached to fluoride.

Ken I am not at this time suggesting to include parental incomes in this study.

My point is that that concept illustrates that an important smaller part of a distribution can have its effect masked by the larger part.

Xiang’s data is more numerous at lower fluoride levels, and effects at higher fluoride levels, where fewer subjects were residing, can be more fairly acknowledged if their category is given a fair weight.

Lin FF et al did not afford space in their article to give a full description of their stratified sampling of the groups of 10 to 12 chose from the 60 or so likely members of each of the 12 classes. They would have wanted to be sure that randomly choosing 20% of the class for further testing did not produce a sample without a representative age profile, or sex profile for example. So they would have stratified first, into sex and age groups and then chosen randomly from those strata.

What I see being done with Connett’s presentation is just Xiang’s stratification. Where specifically in Xiang’s work does Connett’s abstraction point show?

Ken wrote: “Why are you opposed to inclusion of parental incomes and child poverty in such regression analyses? Surely these are more likely to be relevant to IQ than is fluoride?”

I am not opposed, just at the moment I brought up that subject as a parallel.

I could give other parallels of the statistical picture but someone may try to accuse me of or even possibly use the technique Naomi Orestes described, in the video you ctied, of trying to sustain confusion, as in obfuscating global warming.

Where in Xiang’s reports did Connett get the stratified water F chart?

I know I have been using the stratification concept a bit differently.

Please think of how WINZ pays people over 65 years of age. Every NZer gets Super based on age alone, but persons living alone get extra, if their other income is not too high I think. An average payment figure for the whole over 65 population is useful in some respects but does not offer as much info as the stratified one.

Thanks, Ken. Your Apr 23, 2015 statement: “First of all the figure shows what Xiang’s data is like. It compares IQ with urine fluoride concentration – unfortunately he did not give a similar figure for fluoride concentration in drinking water” misled me. I had thought you meant he did not give water fluoride figures, though you actually meant a figure or graph.

The UF/IQ graph has many values in the low UF range, which would be Xinhuai.

It is possible to get a good feeling for what the WF/IQ “figure” would look like by examining Table 8 in the Apr 23 link to Xiang’s paper you gave.
Xinhuai with low fluoride had 290 children, then Wamiao with higher fluoride was divided into 5 groups, but totalling only 222 children. Connett has plotted the Table 8 figures, and you pasted in his plot.

This is Table 8, but leaving out the +/- errors which you can read in the paper
Group——Number of children—-Water F—IQ
Xinhuai———–290———————0.36——100.41
Wamaio A——–9————————0.75——99.56
B———————42———————-1.53——95.21
C——————–111———————-2.46——92.19
D———————-52———————-3.28——89.88
E————————8———————–4.16——78.38

Now could you please say is it Xiang’s displaying of his data like this which is “dishonest”, or is it Connett’s graphing of it, or his way of presenting the graph?

For it appears you prefer a correlation like Xiang’s for UF/IQ in which the large number of Xinhuai figures mask the Wamiao range.

Both Xiang and Connett were and are dishonest. Both of them are aware of the poor correlation with urinary F and I find it hard to believe Xiang had not done a similar regression for water F. My enquiries in this issue got a silence from Xiang and a rude âgo awayâ from Connett. Guilty as sin, I would say.

On the other hand a reasonable journal would not have accepted the paper without querying the lack of regression for water F (but Fluoride is a crappy journal with effectively non-existent peer review).

You should not make assumptions like âmany values in the low UF range, which would be Xinhuai.â as it is not warranted at all. However, the key thing is the large variance as you can see for low values of F the IQ varies dramatically. But that is what you expect from an R2 value as low as 3%. The honest interpreter accepts the values as they are.

Of course I prefer a proper regression analysis to an artificial manufactured curve. It is stupid to talk about an honest presentation of all the data as âmaskingâ just the data you want to select. One should always look at all the data and be very careful about removing any â no matter how tempting it is â without extremely good reasons.

I have found with the statisticians I have worked with that the first thing they wanted to do with my data is to see a plot of the whole data set. Peer-reviewers who a statistically capable always ask to see such plots as well.

Connett has been dishonestly outing lipstick on a pig by pretending that the correlation is much better than it really easy. That is extremely easy to do with any set of data where there is a significant trend. It as a way of hiding the very low R2 value and the obvious variance which shows up when the whole data set is plotted.

As for the urinary fluoride/IQ relationship, to me it seems to be in two regions which meet at about 3.5 mg/L, which could be about 2.5 mg/L water fluoride from Xiang’s figures. The first part has a slightly greater negative correlation than the simple straight line. The second part has a slightly positive correlation. Posting in the off chance it means anything.

Wow, what a random scatter. A human would not be able to draw any correlation lines through it. So you took a computer, which can draw a line through any graph with two or more points, to draw one for you.

I see that both the lowest and highest IQs are found in the lowest fluoride areas. Does that mean that higher fluoride levels reduce the range of IQs, or just that there are fewer people in higher fluoride areas and hence smaller ranges of most measurements?

What it means is that F is probably not influencing IQ and one should look at other factors. Attempts to confirm some sort of weird bias by playing with the data in the way Brian does is just desperate and avoids the obvious.

I think Xiang did have other data which could have been included in the regression so it is a real pity he didnât and that his mates currently discourage him from doing so.

I only found about 246 points and can’t tell which ones are doubled up. Xiang said: “Children for urine testing were chosen by random sampling: in Wamiao, 155 for fluoride and 46 for iodine; in Xinhuai, 135 for fluoride and 40 for iodine.” Stuartg has taught me to add.

But for the first segment rho is -0.1885 and the 95% confidence -0.323 -0.046.
Second segment 0.0574 -0.199 0.306.

However a bit of speculation comes to mind: that heavier tea drinking, as well as increasing the fluoride burden, may also with the caffeine, be overcoming some facet of attention deficit as the prescribed stimulant ritalin does.

Stuartg: “Wow, what a random scatter. A human would not be able to draw any correlation lines through it. So you took a computer, which can draw a line through any graph with two or more points, to draw one for you.”

It is fairly random but when I looked for a bit I saw two main clouds of points.

The single straight line was put in by Xiang.

I read off the points, have them if you want my readings, and put the two clouds into Vassarstats, with the results I have given.

On Xiang’s UF/IQ graph, the part up to about UF= 1.9 mg/L is more dense with points.
My readings from the graph for that region and Vassarstats give
rho -0.1242, R^2 0.0154 (so it can be thought of as UF relates to 1.5% “causation” in that region.) Approximating from Xiang’s Table 9, that should be a region where the drinking water is under 1 mg/L fluoride.

The slope is -0.438213 and IQ intercept is 101.88297.

The 0.95 confidence for rho is -0.288, 0.047, which is hardly going positive.

So with fair confidence, though confounded by tea caffeine and probably other things, IQ is negatively correlated to UF when drinking water is under approx 1 mg/L.

The 0.99 confidence limits are correlation being between -0.337 and 0.1.
That would mean do the whole set of measurements (for UF up to 1.9 mg/L) 1000 times over and something like 10 of those sets could be on those confidence limits for the correlation figure. If I happened to get the -0.337 figure the first time (I out of 100 chance) I would be thinking UF is explaining more than 11% of the IQ loss in that low fluoride range. Or if I were to have got the 0.1 I would be thinking it were explaining 1% of a benefit to IQ from fluoride in the low range.

But I also said “fair confidence,” since it is not quite certain from Xiang’s work that 1.9 mg/L UF relates to less than 1 mg/L water fluoride. Over a large group it might average that way.

So, after all that work, Brian, you are no better off â in fact worse off. As you say, you cannot see a relationship between urinary fluoride and IQ â yet the original data does show a significant relationship explaining 3% of the variance in IQ.

So your extra âanalysisâ actually threw information away.

The way to make progress with Xiangâs data is to include confounders in the regression analysis. At the moment one can only conclude that he hasnât found the cause of IQ decline and it is very unlikely to be F.

Xiang’s Pearson correlation, Ken, which you refer to, is -0.174 and squaring that produces 0.0302767 or just over 3% causal effect regressed over all his UF/IQ data

I have not been able to read all of Xiang’s data and what I get, putting all that I did read in Vassarstats’ Pearson calculator, is -0.1678 and 2.81%, a little bit less.

So I have something like Xiang’s data set for UF/IQ.

Stuartg feels Xiang’s graph looks random, and therefore his claim would be Xiang’s low correlation cannot even be existing?

The quality of the society we live in depends in part on the IQ of people in it.
Like interest on a bank account can a small percent compound?

Iodine has been supplemented, lead has been removed from petrol and paint. Children go to school instead of the work-house pretty much, which helps IQ. Though if family businesses work on a contract system, and risk missing deadlines then children may be got to work, risking byssinosis &c, and losing the play essential for all-round growth. That is a little step backwards. But because it small when averaged over the whole society may it safely be ignored?

Fluoridation is claimed to produce a little step forward in dental health. Some say as much as 30%, though that is challenged. My quick look at Xiang’s UF/IQ data appears to say that for water fluoride levels rather relevant to fluoridation, that in that region my readings from the graph and Vassarstats givea -0.1242 correlation. Squaring that produces 0.0154, so it can be thought of as UF relates to 1.5% “causation” in that region. That is only half than what Xiang gets over the whole range, though advancing as far as water fluoride of about 2.5 mg/L appears to produce a 3.55% negative “cause”, more than Xiang’s. Above that water fluoride level, IQ appears to increase a bit though ti is not making up for the earlier loss.